This invention relates to .beta.-lactam antibiotics. In particular, it relates to certain 3-(substituted)-1-carba(dethia)-3-cephems and cephalosporin esters and to a process for the preparation thereof.
Among the newer .beta.-lactam antibiotics currently under investigation are the 1-carba(1-dethia)-3-cephem-4-carboxylic acids. These .beta.-lactam antibiotics provide significant synthetic challenges. Accordingly, one of the more noteworthy approaches to total synthesis of 1-carba(1-dethia)-3-cephem-4-carboxylic acids is the asymmetric route described by Evans, et al., U.S. Pat. No. 4,665,171. Thus, because these newer .beta.-lactam antibiotics provide such synthetic challenges, the development of new processes are of considerable importance.